The Planet Prison was a superweapon developed by the Galactic Republic during the Cold War with the Sith Empire. It was originally created by Doctor Nasan Godera and weaponized by a team of scientists lead by Doctor Eli Tarnis. The Planet Prison was built as a means to blockade a planet without the use of massive capital ships or brute firepower while still rendering the ability to travel to and from the planet's atmosphere inert. It was designed to utilize ion-like surges to supercharge the planet's outer atmosphere such that any ship passing through it would be disabled.
The original technology for the Planet Prison was passed from Godera to Tarnis when the Republic quietly restarted the Republic Superweapon Initiative, but Tarnis, secretly a Sith Lord, used both the Black Sun and Justicars criminal organizations to steal the plans for the weapon and hand it over to the Empire. However, Tarnis was killed by a the former Padawan of Jedi Master Orgus Din before the Planet Prison could be brought to bear on Coruscant.
Later, the design plans for the Planet Prison were combined with the technology of several different superweapons under the order of Darth Angral, leading to the creation of a world-devastating device known as the Desolator. It would be used to eradicate all life on the Republic agricultural world of Uphrades. Angral intended to utilize the same weapon on the Jedi homeworld of Tython, but was stopped by the Jedi Knight. Any remaining superweapon technology attached to the Desolator was destroyed soon after.